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Edge teeth direction

Just got hold my Devin ITK... and I couldn't be happier! After looking at it for 10 mins, I tried to test how sharp OOTB with the paper test (passed) and then 3 finger test... and the first impression was, "hmmmm.... nope... fingers are sliding = not sharp...

But that was when I slid my fingers towards the handle.. but when I slid my fingers towards the tip, the edge dug a bit into my finger tips almost instantly...

Then I recalled when Murray Carter was talking about taking into consideration the direction of your edge's teeth when sharpening.... That if your cutting style is pulling the knife towards you, the teeth should point towards the handle... and if your style is to push the knife forward when cutting, then the teeth should point towards the tip...

I don't know if this is the reason some knives feel very sharp when you slice a tomato, but won't push cut... maybe because the teeth aren't pointed straight down, but are pointed either towards the tip or heel....

Wow...this is spooky. While at work, I was just thinking about how I might touch up my funayuki and I plan on finishing with tip to heel strokes, because I have a slight draw on my cutting action. It's turned into a straight up, slight pull back and down motion, and I figured "tooth direction" might aid in an even better cutting knife...
So, yes I think this makes a lot of sense.

yeah, I actually just realized this after experiencing it myself... I'm also wondering what effect "stropping on balsa, leather or other surfaces" have on the direction of the teeth... does it straighten them or do they even affect their direction at all...

TK and I talked about this in a different thread a month or so ago. He wanted to sharpen 2 identical knives with opposite direction strokes and see if someone could tell the difference in a blind test. Tip to heel strokes for the drawing/pulling action on a suji, and sectional sharpening for a gyuto? Would finishing strokes be enough to develop a noticeable scratch pattern, or would you have to keep the direction the same through out the progression? You normally still have 1k, 3k, etc scratches even when finishing at 5k (or whatever). The DT was probably finished on a belt, pretty easy to control direction of the teeth on that.

You may vary the teeth direction between both sides as well, resulting in a very aggressive edge. I don't know yet if it is durable.

This is actually what got me started thinking about it. I'd still like to try blind testing. So far, I think I can tell the difference but it isn't a huge difference, at least not the way I've been sharpening lately.

I thought I'd quantify. After the 5k plus 0.25 micron diamond strop, carefully scratching in only one direction (same on both sides), slicing in one direction instantly bites into a tomato over a few dozen slices. Slicing in the other direction, the knife slides maybe a couple of mm consistently over a few dozen slices before biting. Maybe more extreme angles would yield a more pronounced difference.

I think that's what Benuser is describing. I haven't tried to do any careful observation on that yet but I used to sharpen that way and going to the hand-switching method, I wondered if the quality of my edges was changing.